1. Field of the Invention
The present invention relates to a method of manufacturing a nitride semiconductor light emitting device, and more particularly, to a method of manufacturing a nitride semiconductor light emitting device, the method minimizing deformation of and thermal damage to a light emitting structure in a process of removing a substrate from the light emitting structure, thereby improving the light extraction efficiency, and to a nitride semiconductor light emitting device manufactured by the method.
2. Description of the Related Art
In general, the nitride single crystals constituting a group III nitride semiconductor light emitting device are formed on a particular substrate for single-crystal growth such as a sapphire or SiC substrate. However, using an insulating substrate such as a sapphire substrate greatly restricts the arrangement of electrodes. That is, in the conventional nitride semiconductor light emitting device, the electrodes are arranged horizontally, narrowing the current flow. Due to such narrow current flow, the forward voltage Vf of the light emitting device increases, decreasing the current efficiency of the device and rendering the device vulnerable to electrostatic discharge.
To solve such a problem, a nitride semiconductor light emitting device having a vertical structure is required. However, the nitride semiconductor light emitting device requires a process of removing an insulating substrate such as a sapphire substrate to form electrodes on upper and lower surfaces thereof.
FIG. 1 is a cross-sectional view illustrating a process of removing a sapphire substrate from a light emitting structure according to the prior art. As shown in FIG. 1, the sapphire substrate 11 is removed by a laser lift-off process after attaching a conductive substrate 14 on a nitride single-crystal light emitting structure 12 by using a conductive adhesive layer 13. However, the sapphire has a thermal expansion coefficient of about 7.5×10−6/K whereas the GaN single crystal, which is the main material of the light emitting structure 12, has a thermal expansion coefficient of about 5.9×10−6/K. Therefore, a lattice mismatch of about 16% occurs.
Due to such a lattice mismatch, the heat generated from a process of emitting a laser beam to the sapphire substrate 11 is transferred laterally along the sapphire substrate 11. Therefore, thermal stress is generated along the interface of the sapphire substrate 11 and the light emitting structure 12, which problematically increases the likelihood of damage to the nitride single crystals. This resultantly degrades the luminance and reliability of the nitride semiconductor light emitting device.